1. Field of the Invention
The present invention relates to a deflection yoke assembled to a cathode ray tube (CRT) for use in, for example, a television receiver and a monitor display, and more particularly to the mounting of a balance coil for a horizontal deflection coil.
2. Description of the Related Art
It is well known that a deflection yoke is assembled to a CRT for a television receiver and a monitor display and operates to deflect electronic beams both in a horizontal direction and in a vertical direction.
FIG. 9 is a side view of a conventional deflection yoke, showing only a pertinent portion required for generating a deflection magnetic field. A horizontal yoke coil is a coil that causes R, G, and B electron beams of the CRT to deflect in a horizontal direction. The horizontal yoke coil includes two vertically disposed coils: an upper horizontal yoke coil 1a and a lower horizontal yoke coil 1b supported on a bobbin 3. The bobbin 3 has grooves, depicted in dotted lines, in which the horizontal yoke coils 1a and 1b are wound. The bobbin 3 serves as a spacer to insulate the horizontal yoke coil from other coils and also supports the entire deflection yoke thereon. An adjustment core 6 is used to adjust the balance between the upper and lower coils 1a and 1b. Reference numeral 7 denotes a vertical deflection coil and numeral 8 denotes a core that controls the deflection magnetic field. A printed circuit board 9 receives leads 10 that are led out of the vertical coil 7, the end portions 11a and 11b of the upper and lower coils 1a and 1b. The balance coil 13 for adjusting the horizontal deflection magnetic field is wound on the bobbin 12.
As shown in FIG. 9, the deflection yoke includes a pair of upper and lower coils 1a and 1b, the vertical coil 7, the core 8, the bobbin 12, a balance coil unit that includes the coil 13 and adjustment core 6, the leads 10, 11a, and 11b of the various coils, and the printed circuit board 9.
FIG. 10 illustrates the structure of the balance coil unit. The bobbin 12 is formed of a resin material and has two coil sections aligned in line with each other. The balance coil 13 is wound around the coil sections. The adjustment core 6 is inserted into the bobbin 12 and moved back and forth to change the position of the adjustment core 6, thereby adjusting the inductance value of the balance coil 13. The bobbin 12 is mounted on the printed circuit board 9 with its legs inserted into the printed circuit board 9 in FIG. 9. The balance coil unit has lead wires that are electrically connected to the end portions 11a and 11b of the horizontal deflection coil 1a and 1b, respectively. The balance coil unit has further lead wires that are electrically connected to a terminal 2a. The printed circuit board 9 receives these lead wires of the balance coil unit.
FIG. 11 illustrates electrical connection for generating the horizontal deflection magnetic field.
Referring to FIG. 11, the upper and lower coils 1a and 1b have one ends connected to the terminal 2b and the other ends connected to the balance coil 13. Two wires are led out from a substantially mid point of the balance coil 13 and connected to the terminal 2a. A horizontal drive circuit, not shown, provides a current, which generates the horizontal deflection magnetic field, through the terminals 2a and 2b to the upper and lower coils 1a and 1b. 
As shown in FIG. 9, the balance coil unit is disposed on a side of the printed circuit board 9 opposite to a side on which wiring patterns are formed. The lead wires of the balance coil unit in FIG. 10 are connected to the wiring patterns through the terminal boards and grommets mounted on the printed circuit board 9. External forces are often exerted to the horizontal coil and balance coil, and a large current flows through these coils. Thus, in order to comply with safe standards, the grommets are required to electrically connect to the wiring patterns formed on the circuit board 9.
With the conventional deflection yoke of the aforementioned construction, the balance coil 13 and the wiring patterns are disposed on the same side of the circuit board 9 as shown in FIG. 10. This configuration is disadvantageous in reflow soldering. Therefore, an expensive double-sided printed circuit board with through-holes or grommets has to be employed.
Further, many terminals require hand-soldering. The heat capacity of an soldering iron is only about 2000 Kcal and takes about 5-6 seconds to solder one terminal. This is very inefficient.
When a reflow soldering apparatus is used, the resin-molded coil bobbin can melt since the coil bobbin 12 comes into contact with the melted solder with the result that the resin molded coil bobbin melts. In order to prevent this problem, the balance coil unit is first dismounted from the printed circuit board 9, and then a preparatory work is done to prevent the parts-receiving holes in the printed circuit board 9 from being clogged with solder. Finally, hand soldering is required for soldering on the other side of the printed circuit board 9. Alternatively, the lead wires may be soldered simultaneously. This simultaneous soldering operation, of course, reduces the time required for soldering but requires additional operations for separating the balance coil unit from the printed circuit board 9 and for replacing the balance coil unit to the printed circuit board 9.
Japanese Patent Preliminary Publication (KOKAI) No. 08-250042 discloses one such deflection yoke having the aforementioned drawbacks. With the disclosed deflection yoke, a horizontal deflection coil and a balance coil are mounted on the same side of the printed circuit board 9. Lead wires from the respective coils are led out from the same side of the printed circuit board 9 and soldered by using a reflow soldering apparatus. However, a preparatory work was required for the lead wires of the horizontal coils and balance coil before they are subjected to reflow soldering.
The present invention was made in view of the aforementioned drawbacks of the conventional art.
An object of the invention is to simplify the wiring operation for a horizontal deflection coil and a balance coil, and improve reliability of the deflection yoke.
A deflection yoke has a pair of vertical deflection coils as well as first and second horizontal deflection coils. The first and second horizontal deflection coils are aligned vertically and mounted to a cathode ray tube. The first and second horizontal deflection coils surrounds a cylindrical core formed to extend along the neck of the cathode ray tube. A balance coil is connected in series with the first and second horizontal deflection coils and has an adjustable inductance. The deflection yoke includes a first bobbin as first supporting means and a second bobbin as second supporting means. The first bobbin supports the first and second horizontal deflection coils each of which has a first coil-end lead and a second coil-end lead. The second bobbin supports the balance coil thereon. The first bobbin and second bobbin are formed in one-piece construction with each other. The first coil-end lead of the first horizontal deflection coil (1a) and the second coil-end lead of the second horizontal deflection coil are wound around the second bobbin to form the balance coil such that the balance coil is formed continuous with horizontal deflection coils.
The first and second horizontal deflection coils may be formed of a solid wire.
The first and second horizontal deflection coils may be formed of a plurality of wires. For example, the first and second horizontal deflection coils are formed of litz wire.
After the first and second horizontal deflection coils and the balance coil have been wound around the respective bobbins, the second bobbin is separated from the first bobbin and than the second bobbin is mounted to a desired part of the first bobbin.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.